Low-bursting-rate pure titanium seamless pipe for metal corrugated pipe and production process of low-bursting-rate pure titanium seamless pipe

Abstract

The invention relates to a low-bursting-rate pure titanium seamless pipe for a metal corrugated pipe and a production process of the low-bursting-rate pure titanium seamless pipe The seamless pipe ischaracterized in that the seamless pipe has the grain size of 6-7 levels, the tensile strength Rm is larger than or equal to 300 MPa and smaller than or equal to 400 MPa, the yield strength Rp0.2 is larger than or equal to 180 MPa and smaller than or equal to 310 MPa, the ductility is larger than or equal to 50%, the wall thickness is uniform and is +/-5%t, the limit flaring rate is larger than orequal to 60%, and the bursting rate is smaller than or equal to 3%. According to the pure titanium seamless pipe prepared through the method, the grain size reaches the 6-7 levels, the room-temperature ductility reaches 50% or above, the wall thickness deviation is controlled to be +/-5%t, the limit flaring rate reaches 60% or above, and the bursting rate in subsequent corrugated pipe preparationcan be 3% or below.

Description

technical field [0001] The invention relates to a pure titanium seamless pipe with low bursting rate for metal bellows and a production process thereof. Background technique [0002] Metal bellows is a flexible, thin-walled, transversely corrugated shell part that can produce axial, angular, lateral and combined displacements under the action of external forces. It can be used as a sensitive element, a shock absorbing element, and a compensating element , sealing components, valve components and pipeline connectors, which have the functions of compensating pipeline thermal deformation, shock absorption, and absorbing pipeline settlement deformation, are widely used in petrochemical, instrumentation, aerospace, chemical, electric power, cement, metallurgy and other industries. The material for making metal bellows should not only have good compatibility with the temperature and corrosion of the working environment, but also need to have high strength and long fatigue life, an...

AI Technical Summary

Problems solved by technology

[0005] (1) There are metallurgical defects such as composition segregation or inclusions inside the blank pipe used: affected by the uniform distribution of impurity elements in sponge titanium, changes in cooling conditions, molten pool shape and depth during the smelting process, and the distribution of impurity elements during solidification and crystallization Influenced by factors such as different coefficients, it is inevitable that there will be differences in the local distribution of impurity elements in the billet to form segregation; the sponge titanium contains defective titanium blocks such as nitrides or foreign matter such as organic matter, which are brought into the process of electrode preparation, welding and smelting. The high melting point metal or non-metallic compound, as well as the incomplete penetration of the electrode due to material loss, etc., form inclusion defects in the billet that are significantly different from the matrix structure. The inclusions are usually divided into high density by density (such as tungsten, tungsten, Molybdenum, niobium, etc.) and low-density (such as titanium nitride, oxide, carbon and carbide, non-penetrated electrodes, etc.) inclusions, the inclusions usually have a high melting point, and it is difficult to eliminate during smelting

[0006] (2) The elongation rate of the blank pipe used at room temperature is not high enough: the elongation rate of the pipe at room temperature is critical to the preparation of corrugated pipes, and it is an important factor affecting the hydroforming limit and forming working pressure

At present, the room temperature elongation of pure titanium seamless pipe is not high enough, generally 30% to 40%, which is not conducive to the preparation of bellows by hydraulic bulging

[0007] (3) The uniformity of the wall thickness of the blank pipe used is not good enough: during the hydraulic bulging process of the metal bellows, the deviation of the wall thickness will cause uneven cold hardening at the trough, aggravate the uneven distribution of deformation stress, and easily lead to rupture. Therefore, the preparation of metal bellows has strict requirements on the uniformity of the wall thickness of the raw material, and it is advisable to achieve ±5%t (t is the nominal wall thickness). At present, the wall thickness deviation of seamless pipes is generally controlled within the range of ±10%t

[0008] (4) The process performance of the blank pipe used is not good enough: the limit expansion rate is one of the important indicators to measure the process performance of the pipe. The greater the limit expansion rate, the better the process performance of the pipe

At present, the limit expansion rate of pure titanium seamless pipe is not high enough, generally around 45%.